1. Field of the Invention
The present invention relates to a memory device using semiconductor characteristics.
2. Description of the Related Art
Dynamic random access memory (DRAM) with a memory cell including one capacitor and one transistor (also referred to as a cell transistor) is widely used as a typical memory device.
Note that in this specification, a memory cell indicates a circuit configuration needed for holding a minimum unit of data, and a memory device indicates a semiconductor device including at least integrated memory cells.
A planar transistor has been conventionally used to form a DRAM; however, a method using a recessed channel array transistor (RCAT) in which a gate is arranged three-dimensionally so as to prevent leakage current due to a short-channel effect caused by miniaturization of a circuit is now employed (see Non-Patent Document 1).